In a small frying pan over medium high heat, cook pancetta until crisp, stirring often, 2-3 minutes. Transfer to a paper towel to drain. Discard all but 1/2 tablespoon fat from pan. Add shallot and stir over medium high heat until soft, 1-2 minutes. Remove from heat and whisk in oil, vinegar, mustard and thyme. Season with salt and pepper. Put spinach and sliced pear in a large bowl and gently toss with dressing. Arrange salad on plate. Crumble goat cheese on top and sprinkle with pancetta.